You pull the weed, and it breaks off at the roots. You plunge your hand into the loam, grasping about for the scattered roots, never finding them all. This season or next, alas, the weed will be back. You might even damage some good plants with all the effort.

Cancer's kind of like that. Physicians now have drugs to kill most kinds of cancers, and they're getting better at targeting the drugs to strike only tumor cells, rather than healthy ones nearby.

But nothing in a doctor's arsenal can kill the roots of cancer, the stem cells. That's why a cancer can be put into remission, but the threat of its return remains.

Not only can doctors not kill cancer stem cells, they can't even reliably find them. In fact, they don't know what they look like. Or even how big the cells are.

So it might seem a bit audacious that a Houston scientist believes that, within the next five years, he can build a sophisticated computer model of the behavior of these mysterious cells in a living system.

Step 1: Identify the cells

For the purposes of the grant the researchers will focus on breast-cancer stem cells, which turn into breast cancer cells and ultimately tumors. Like other cancer stem cells, breast-cancer stem cells have proved resistant to all types of drug therapy.

The scientists' first step will be to use various new high-resolution microscopes to identify and characterize the cancer stem cells.

(The microscopes almost defy description, but they have great science-fiction-sounding names like “multi-photon laser scanning microscope,” which seems like it should be used to blast a Klingon cruiser.)

As they experiment with the stem cells, the researchers will begin to develop mathematical, or computational, models that will use data collected in their lab to emulate the behavior of the cells. Further feedback from the biological experiments will be used to refine the models.

Eventually, Wong said, the goal is to have a model that can predict how cancer stem cells develop and respond to various stimuli in their natural, biological environment.

Step 2: Screen drugs

With such a model in hand, the scientists believe they can then begin to screen new and existing drugs to identify compounds that might be able to kill stem cells, or somehow get them to turn into cancer cells, which can be killed by chemotherapy.

“The whole idea is to really be able to come up with a computational model that can predict drug response,” Wong said.

Although scientists long suspected the existence of cancer stem cells, it wasn't until 1997 that Canadian scientist John Dick identified them conclusively in leukemia patients, and only in recent years have the cells been identified in other cancers based upon proteins and other biological markers on their surface.

Now, with their powerful genetic, imaging and computational tools, scientists are seeking to use this knowledge to eradicate cancer at its roots.

Michael Lewis, a Baylor molecular biologist who will collaborate with Wong on the new project, said he believes identifying all of the biological proteins associated with breast-cancer stem cells will probably be the project's biggest contribution.